As compared with a cathode ray tube (CRT) display, a liquid crystal display (LCD) has many advantages such as a small thickness and a low power consumption. Therefore, the liquid crystal display has replaced the CRT display in various fields. As a passive light-emitting display, the liquid crystal display requires a thin backlight with uniform luminance and high energy efficiency. A white light emitting diode (LED) backlight, owing to its prominent merits, is gradually substituting for the cold cathode fluorescent lamp (CCFL) techniques and becoming the mainstream backlight for the existing liquid crystal displays.
However, as for a backlight in an existing liquid crystal display device, the spectrum comprises a large amount of high-energy and short-wave blue light at irregular frequencies with a wavelength smaller than 450 nm. The short-wave blue light has extremely high energy and can penetrate through the lens and impinge on the retina directly. When the blue light irradiates the retina, free radicals are generated to cause contabescence of the retinal pigment epithelial cells, which may result in nutrient inadequacy of the photosensitive cells and thus lead to impairment of vision.
White light does not exist on its own in the nature. Blue light is an important component of the visible light spectrum, and is mixed with green light and red light to present white light. At present, according to a conventional process for a white light LED, phosphorous powder is added into a blue chip. The blue light is used as an excitation light, and the shorter the wavelength is, the stronger excitation capacity it has; and after the blue light excites the phosphorous powder coated on the surface of the chip, light of a corresponding color is emitted, and then interacts with the blue light to provide a synthesized white light by color mixture. Among the spectrum of a conventional white light LED backlight, blue light with a wavelength between 430 nm and 450 nm is the most harmful to human eyes.
In order to improve the blue light radiation and reduce its harm to the human eyes, anti-blue light radiation lens are designed in the prior art. These types of lens can reach a filtering effect of 40% to 50% with respect to blue light with a wavelength at 400 nm-500 nm. Although these types of lens can reduce the amount of harmful blue light in the backlight to a certain degree and thereby protect eyes of the user, such design has the following disadvantages. (a) The film structure is complicated, which results in difficulties in processing. (b) The blue light is absorbed in a large range, the loss of blue light between 400 nm and 500 nm is considerable, and this will affect the visual effect and the display gamut. (c) Dedicated glasses for filtering the blue light are worn, which are worn by one person only, influencing the visual experience of the human eyes and bringing a poorer viewing effect.
To sum up, when harmful blue light in the backlight is reduced according to the prior art, the manufacture process is difficult, and the range of blue light to be absorbed is large, which influences the display quality of the product.